Function Of Programmed Death-1 Research Articles

Research progress of therapeutic effects and drug resistance of immunotherapy based on PD-1/PD-L1 blockade.

The binding of programmed death-1 (PD-1) on the surface of T cells and PD-1 ligand 1 (PD-L1) on tumor cells can prevent the immune-killing effect of T cells on tumor cells and promote the immune escape of tumor cells. Therefore, immune checkpoint blockade targeting PD-1/PD-L1 is a reliable tumor therapy with remarkable efficacy. However, the main challenges of this therapy are low response rate and acquired resistance, so that the outcomes of this therapy are usually unsatisfactory. This review begins with the description of biological structure of the PD-1/PD-L1 immune checkpoint and its role in a variety of cells. Subsequently, the therapeutic effects of immune checkpoint blockers (PD-1 / PD-L1 inhibitors) in various tumors were introduced and analyzed, and the reasons affecting the function of PD-1/PD-L1 were systematically analyzed. Then, we focused on analyzing, sorting out and introducing the possible underlying mechanisms of primary and acquired resistance to PD-1/PD-L1 blockade including abnormal expression of PD-1/PD-L1 and some factors, immune-related pathways, tumor immune microenvironment, and T cell dysfunction and others. Finally, promising therapeutic strategies to sensitize the resistant patients with PD-1/PD-L1 blockade treatment were described. This review is aimed at providing guidance for the treatment of various tumors, and highlighting the drug resistance mechanisms to offer directions for future tumor treatment and improvement of patient prognosis.

Combinatorial Strategies With PD-1/PD-L1 Immune Checkpoint Blockade for Breast Cancer Therapy: Mechanisms and Clinical Outcomes.

As an emerging antitumor strategy, immune checkpoint therapy is one of the most promising anticancer therapies due to its long response duration. Antibodies against the programmed death-1 (PD-1) and programmed death ligand-1 (PD-L1) axis have been extensively applied to various cancers and have demonstrated unprecedented efficacy. Nevertheless, a poor response to monotherapy with anti-PD-1/PD-L1 has been observed in metastatic breast cancer. Combination therapy with other standard treatments is expected to overcome this limitation of PD-1/PD-L1 blockade in the treatment of breast cancer. In the present review, we first illustrate the biological functions of PD-1/PD-L1 and their role in maintaining immune homeostasis as well as protecting against immune-mediated tissue damage in a variety of microenvironments. Several combination therapy strategies for the combination of PD-1/PD-L1 blockade with standard treatment modalities have been proposed to solve the limitations of anti-PD-1/PD-L1 treatment, including chemotherapy, radiotherapy, targeted therapy, antiangiogenic therapy, and other immunotherapies. The corresponding clinical trials provide valuable estimates of treatment effects. Notably, several combination options significantly improve the response and efficacy of PD-1/PD-L1 blockade. This review provides a PD-1/PD-L1 clinical trial landscape survey in breast cancer to guide the development of more effective and less toxic combination therapies.

Measurement of soluble PD-1 and soluble PD-L1 as well as PD-L1 and PD-1 from perioperative patients with gastric carcinoma.

Till now, no experiment has been performed to detect programmed death ligand 1 (PD-L1)/programmed death 1 (PD-1), soluble PD-L1/soluble PD-1 simultaneously in perioperative patients of gastric carcinoma. Our experiment aims at determining the clinical significance and possible mechanism of soluble PD-L1/soluble PD-1 in gastric carcinoma. Thirty patients undergone gastrectomy were selected as the experimental group. Tissue's programmed death ligand 1 and peripheral programmed death 1 were detected using immunofluorescence and flow cytometry. Soluble PD-L1 and soluble PD-1 were detected using enzyme-linked immunosorbent assay. First, preoperative programmed death 1 was higher than control group and decreased to normal post-operatively. Preoperatively ,elevated levels of programmed death 1 on cluster of differentiation (CD)4 T cells indicated less lymphatic metastasis (P<0.01) and small tumor volume (P<0.01); elevated programmed death 1 of CD8 T cells indicated big tumor volume (P<0.01) and well histological differentiation (P<0.01). Second, preoperative soluble PD-L1 and soluble PD-1 are lower than in control group. Post-operatively, the soluble PD-1 rose to normal, but the soluble PD-L1 showed no change. Third, programmed death ligand 1 can be observed in carcinoma tissue. Fourth, the area under the curve of soluble PD-1 (0.675) for diagnosis was worse than that of soluble PD-L1 (0.885). Kaplan-Meier analysis showed that soluble PD-1<245.26pg/ml in post-operative serum predicted a poor prognosis (overall survival percentage: 60%) at 2 years (P<0.05). Multivariate analysis revealed that carcinoembryonic antigen (>5ng/l) and soluble PD-1 after gastrectomy (>245.26pg/ml) were independent prognostic factors for overall survival (hazard ratio: 20.812, 95% confidence interval: 1.217-355.916, P=0.036; hazard ratio: 0.028, 95% confidence interval: 0.001-0.786, P=0.036, respectively). We propose that soluble PD-1 combined with programmed death ligand 1 are effective not only in protecting T cells from the adhesion by programmed death ligand 1 but also in preventing the occurrence and the development of tumor as well. Through multivariate analysis, we found that soluble PD-1 was an independent protective factor for post-operative prognosis of gastric carcinoma patients, which indirectly verified the vital function of soluble PD-1. Soluble PD-1 might be promising predictive biomarkers for the diagnosis and prognosis of gastric carcinoma patients.

Acute Myeloid Leukemia Cell-Intrinsic PD-1 Functions Promoting Leukemia Development By Recruiting SHP2

Acute myeloid leukemia (AML) is a devastating hematopoietic malignancy. With current therapies, only approximately 30% of patients achieve long-term survival. Therefore, novel, more active and less toxic treatments are urgently needed. Programmed death-1 (PD-1) is a cell surface receptor that functions as a T cell checkpoint and plays a central role in regulating T cell exhaustion. Binding of PD-1 to its ligand, programmed death-ligand 1 (PD-L1), activates downstream signaling pathways and inhibits T cell activation. Abnormally high PD-L1 expression on tumor cells and antigen-presenting cells in the tumor microenvironment mediates tumor immune escape, and PD-1/PD-L1 immune checkpoint blockade has showed promising results in cancer patients. Recently, PD-1 expressed on melanoma cells was also shown to play a pivotal role in tumor growth. To date, in AML, the function of PD-1 has been mainly studied in the host T cells, while little is known regarding the role of PD-1 in AML cells. Herein, we examined the level and role of PD-1 in AML cells using AML murine model and patient samples.We used MLL PTD/WT/Flt3 ITD/ITD knock-in mouse in B6 background, a well characterized AML model, to study the expression and function of PD-1 in AML. Flow cytometric analysis of LSK (Lin -Sca-l1 +c-kit +) cells from the bone marrow (BM) of wild-type (WT, n=5) and AML (n=10) mice showed that 20.9%-61.9% of AML LSKs versus (vs) <5.0% of normal LSKs are PD-1 positive (P< 0.0001). Western blot and Q-RT-PCR analysis confirmed higher levels of PD-1 in AML LSKs than in normal LSKs. The PD-1 levels on LSKs increased over time and associated with disease progression. Similar results were obtained in AML patients, showing PD-1 + in 0.2%-14.6% of AML CD34 + cells vs < 1.0% of normal CD34 + cells (P< 0.05). Data analysis based on TCGA showed that higher PD-1 levels are associated with shorter survival in AML patients (P=0.0125).To assess the functional role of PD-1 in AML, we sorted PD-1 + and PD-1 - fractions fromAML LSKs and observed a lower frequency of quiescent cells (G0, 16.60% vs 44.87%, P< 0.05) and a higher cell growth rate in the PD-1 + vs PD-1 - cells. Further in vivo study showed that PD-1 + AML LSKs (CD45.2) generated higher white blood cell (WBC) counts (P< 0.0001), higher AML engraftment (P< 0.0001) and a shorter survival (median survival 57.5 vs >75 days, P< 0.001) in recipient mice (CD45.1) compared with PD-1 - AML LSKs. Similar results were observed in human samples. Compared to PD-1 - CD34 + cells, PD-1 + CD34 + cells are less quiescent and more proliferative (P< 0.01). PD-1 + AML blasts had higher engraftment rate (13.18% vs 2.68%, p=0.0002) and shorter survival (median survival: 27 vs 45 days, P= 0.0008) in NSGS mice than PD-1 - AML blasts.To evaluate if these in vivo differences observed in PD-1 + vs PD-1 - AML LSKs were mediated by interactions between PD-1 + AML and T cells, PD-1 + and PD-1 -LSKs from AML mouse were transplanted into T-, B- cell-deficient NSG mice. Recipient mice transplanted with PD-1 + AML LSKs had higher WBC counts (P< 0.01), higher AML engraftment (P< 0.0001) and a shorter survival (median survival: 76 vs >130 days, P< 0.0001) than recipients with PD-1 - AML LSKs, suggesting that these differences were T cell-independent.Next, we examined whether blocking PD-1 could affect leukemic cell growth. We sorted LSK cells from AML mice and performed colony forming cell (CFC) assay in the presence of anti-PD1 antibody or isotype antibody. Blocking PD-1 with anti-PD-1 antibody significantly suppressed CFC and cell growth in vitro but did not induce apoptosis compared to isotype control antibody. To explore the molecular mechanism by which PD-1 contributes to AML growth, we then sorted PD-1 + and PD-1 - LSKs from AML mice for molecular studies. Western blot assays revealed higher levels of SHP-2 and phosphorylated (p) -ERK in PD-1 + vs PD-1 - AML LSKs. We validated these results in primary human AML cells by immunofluorescence staining. Confocal microscopy of PD-1 + and PD-1 - human AML CD34 +cells demonstrated that PD-1 localized at the cell membrane and in the cytoplasm and p-ERK was markedly enhanced in the PD-1 + CD34 + cells.In conclusion, we showed here that a subpopulation of murine and human AML blasts expresses high levels of PD-1 which mediated disease initiation and growth through activation of the MAPK/ERK signaling pathways. PD-1 blocking antibody reversed these activities and might contribute to the clinical efficacy of anti-PD-1 therapy in AML. DisclosuresMarcucci: Novartis: Other: Speaker and advisory scientific board meetings; Agios: Other: Speaker and advisory scientific board meetings; Abbvie: Other: Speaker and advisory scientific board meetings.

AB0034 PD-1 AGONISM INHIBITS ACTIVATION OF PLASMACYTOID DENDRITIC CELLS

Background:T cell function is regulated by complex signaling networks of interconnected activators and inhibitors. Blockade of inhibitory receptors such as programmed death-1 (PD-1) has emerged as a novel treatment for multiple forms of cancer. One of the most common adverse events associated with blockade of the endogenous PD-1/PD-L1 pathway is the induction of autoimmune pathology in multiple tissues, demonstrating that PD-1 activation is necessary for normal immune homeostasis in humans (Kostine, et al., 2018). Given this body of clinical data, we sought to develop a PD-1 agonist antibody as a therapeutic approach to restore immune homeostasis in patients living with autoimmune diseases. PD-1 expression and function has been primarily described on T cells (Ishida, et al., 1992), with additional data available from several other immune cell populations (Ohaegbulam, et al., 2015).Objectives:To study the effect of PD-1 agonism on plasmacytoid dendritic cell (pDC) function.Methods:Human PBMCs stimulated with or without toll-like receptor (TLR)-9 agonist, CpG were analyzed by flow cytometry for PD-1 expression on immune cell subsets. To assess the impact of PD-1 agonist on pDC function human PBMCs were activated by CpG in the presence or absence of PD-1 agonist. Type-I interferon (IFN) levels were quantified using ELISA from culture supernatants. The expression of interferon stimulated genes was analyzed by qPCR as a measure of type-I IFN activation.Results:We have discovered that TLR9 activation can induce PD-1 expression on plasmacytoid dendritic cells, which has not been previously reported. Further, we have demonstrated that PD-1 agonism inhibits TLR9-mediated activation and the effector functions of plasmacytoid dendritic cells.Conclusion:These data suggest the potential of PD-1 as a target for regulating diseases with pathology generated by type-I IFN.

Nivolumab Enhances In Vitro Effector Functions of PD-1+ T-Lymphocytes and Leishmania-Infected Human Myeloid Cells in a Host Cell-Dependent Manner.

Functional impairment of T-cells and a concomitant augmented expression of programmed death-1 (PD-1) have been observed in visceral leishmaniasis patients, as well as in experimental models for visceral and cutaneous leishmaniasis. The PD-1/PD-1-ligand (PD-1/PD-L) interaction negatively regulates T-cell effector functions, which are required for parasite control during leishmaniasis. The aim of this study was to elucidate the impact of the PD-1/PD-L axis in a human primary in vitro infection model of Leishmania major (Lm). Blocking the PD-1/PD-L interaction with nivolumab increased T-cell proliferation and release of the proinflammatory cytokines TNFα and IFNγ during the cocultivation of Lm-infected human monocyte-derived macrophages (hMDMs) or dendritic cells (hMDDC) with autologous PD-1+-lymphocytes. As a consequence Lm infection decreased, being the most pronounced in hMDDC, compared to proinflammatory hMDM1 and anti-inflammatory hMDM2. Focusing on hMDDC, we could partially reverse effects mediated by PD-1 blockade by neutralizing TNFα but not by neutralizing IFNγ. Furthermore, PD-1 blockade increased intracellular expression of perforin, granulysin, and granzymes in proliferating CD4+-T-cells, which might be implicated in reduction of Lm-infected cells. In all, our data describe an important role for the PD-1/PD-L axis upon Lm infection using a human primary cell system. These data contribute to a better understanding of the PD-1-induced T-cell impairment during disease and its influence on immune effector mechanisms to combat Lm infection.

PD-1 is a haploinsufficient suppressor of T cell lymphomagenesis.

T cell non-Hodgkin lymphomas (T-NHLs) represent a heterogeneous group of highly aggressive malignancies with poor clinical outcomes1. T-NHLs originate from peripheral T lymphocytes and are frequently characterized by genetic gain-of-function variants in T cell antigen receptor (TCR) signalling molecules1–4. Although these oncogenic alterations are thought to drive TCR pathways to induce chronic proliferation and survival programmes, it remains unclear whether T cells harbour tumour suppressors that can counteract these events. Using a murine model of human T cell lymphoma, we demonstrate that the acute enforcement of oncogenic TCR signalling in lymphocytes drives the strong expansion of these cells in vivo. However, this response is short-lived and robustly counteracted by cell-intrinsic mechanisms. A subsequent genome-wide in vivo screen using T cell-specific transposon mutagenesis identified PDCD1, which encodes the inhibitory receptor Programmed Death-1 (PD-1), as a master gene suppressing oncogenic T cell signalling. Mono- and bi-allelic PDCD1 deletions are also recurrently observed in human T cell lymphomas with frequencies that can exceed 30%, indicating high clinical relevance. Mechanistically, PD-1 activity enhances PTEN levels and attenuates AKT and PKC signalling in pre-malignant cells. In contrast, a homo- or heterozygous deletion of PD-1 allows unrestricted T cell growth after an oncogenic insult and leads to the rapid development of highly aggressive lymphomas in vivo that are readily transplantable to recipients. Altogether, these results indicate that the inhibitory PD-1 receptor is a potent haploinsufficient tumour suppressor in T-NHLs that is frequently altered in human disease. These findings extend the known physiological functions of PD-1 beyond the prevention of immunopathology after antigen-induced T cell activation and have implications for T cell lymphoma therapies and for current strategies that target PD-1 in the broader context of immuno-oncology.

Vaccination with High-Affinity Epitopes Impairs Antitumor Efficacy by Increasing PD-1 Expression on CD8+ T Cells.

Antitumor vaccines encoding self-antigens generally have low immunogenicity in clinical trials. Several approaches are aimed at improving vaccine immunogenicity, including efforts to alter encoded epitopes. Immunization with epitopes altered for increased affinity for the major histocompatibility complex (MHC) or T-cell receptor (TCR) elicits greater numbers of CD8 T cells but inferior antitumor responses. Our previous results suggested that programmed death 1 (PD-1) and its ligand (PD-L1) increased on antigen-specific CD8 T cells and tumor cells, respectively, after high-affinity vaccination. In this report, we use two murine models to investigate whether the dose, MHC affinity, or TCR affinity of an epitope affected the antitumor response via the PD-1/PD-L1 axis. T cells activated with high-affinity epitopes resulted in prolonged APC:T-cell contact time that led to elevated, persistent PD-1 expression, and expression of other checkpoint molecules, in vitro and in vivo Immunization with high-affinity epitopes also decreased antitumor efficacy in the absence of PD-1 blockade. Thus, APC:T-cell contact time can be altered by epitope affinity and lead to therapeutically relevant changes in vaccine efficacy mediated by changes in PD-1 expression. These findings have implications for the use of agents targeting PD-1 expression or function whenever high-affinity CD8 T cells are elicited or supplied by means of vaccination or adoptive transfer. Cancer Immunol Res; 5(8); 630-41. ©2017 AACR.

PD-1 and its ligands are important immune checkpoints in cancer.

Checkpoint programmed death-1 (PD-1)/programmed cell death ligands (PD-Ls) have been identified as negative immunoregulatory molecules that promote immune evasion of tumor cells. The interaction of PD-1 and PD-Ls inhibits the function of T cells and tumor-infiltrating lymphocytes (TIL) while increasing the function of immunosuppressive regulatory T cells (Tregs). This condition causes the tumor cells to evade immune response. Thus, the blockade of PD-1/PD-L1 enhances anti-tumor immunity by reducing the number and/or the suppressive activity of Tregs and by restoring the activity of effector T cells. Furthermore, some monoclonal antibodies blockading PD-1/PD-Ls axis have achieved good effect and received Food and Drug Administration approval. The role of PD-1/PD-Ls in tumors has been well studied, but little is known on the mechanism by which PD-1 blocks T-cell activation. In this study, we provide a brief overview on the discovery and regulatory mechanism of PD-1 and PD-L1 dysregulation in tumors, as well as the function and signaling pathway of PD-1 and its ligands; their roles in tumor evasion and clinical treatment were also studied.

Programmed death-1+ T cells inhibit effector T cells at the pathological site of miliary tuberculosis.

Optimal T cell activation is vital for the successful resolution of microbial infections. Programmed death-1 (PD-1) is a key immune check-point receptor expressed by activated T cells. Aberrant/excessive inhibition mediated by PD-1 may impair host immunity to Mycobacterium tuberculosis infection, leading to disseminated disease such as miliary tuberculosis (MTB). PD-1 mediated inhibition of T cells in pulmonary tuberculosis and TB pleurisy is reported. However, their role in MTB, particularly at the pathological site, remains to be addressed. The objective of this study was to investigate the role of PD-1-PD-ligand 1 (PD-L1) in T cell responses at the pathological site from patients of TB pleurisy and MTB as clinical models of contained and disseminated forms of tuberculosis, respectively. We examined the expression and function of PD-1 and its ligands (PD-L1-PD-L2) on host immune cells among tuberculosis patients. Bronchoalveolar lavage-derived CD3 T cells in MTB expressed PD-1 (54·2 ± 27·4%, P ≥ 0·0009) with significantly higher PD-1 ligand-positive T cells (PD-L1: 19·8 ± 11·8%; P ≥ 0·019, PD-L2: 12·6 ± 6·2%; P ≥ 0·023), CD19+ B cells (PD-L1: 14·4 ± 10·4%; P ≥ 0·042, PD-L2: 2·6 ± 1·43%; not significant) and CD14+ monocytes (PD-L1: 40·2 ± 20·1%; P ≥ 0·047, PD-L2: 22·4 ± 15·6%; P ≥ 0·032) compared with peripheral blood (PB) of MTB and healthy controls. The expression of PD-1 was associated with a diminished number of cells producing effector cytokines interferon (IFN)-γ, tumour necrosis factor (TNF)-α, interleukin (IL)-2 and elevated apoptosis. Locally accumulated Tcells were predominantly PD-1+ -PD-L1+ , and blocking this pathway restores the protective T cell response. We conclude that M. tuberculosis exploits the PD-1 pathway to evade the host immune response by altering the T helper type 1 (Th1) and Th2 balance at the pathological site of MTB, thereby favouring disease dissemination.

Decreased expression of programmed death 1 on peripheral blood lymphocytes disrupts immune homeostasis in peripartum cardiomyopathy

Peripartum cardiomyopathy (PPCM) is a disease of unknown pathogenesis. Programmed death 1 (PD1) has been postulated to modulate immune response through potential mechanisms that remain elusive. This study aimed to elaborate the expression and function of PD1 on peripheral blood lymphocytes (PBLs) in the development of PPCM. Specimens of PBLs were performed to determine the expression of PD1 mRNA using fluorescence quantitative RT-PCR, and Th cytokines by ELISA. Immune homeostasis was evaluated with T lymphocyte phenotypes and immunoglobulin (Ig) isotypes as well as complement factors (C). Morphology of lymphocytes was observed using transmission electronic microscope. Significantly elevated levels of interferon (IFN)-γ, percentages of CD3+, CD4+, CD8+ T lymphocytes, and pro-brain natriuretic peptide (BNP), but reduced levels of interleukin (IL)-4, IgG, IgM, IgA, C3, C4, and left ventricular ejection fraction (LVEF) were detected, which were associated with significantly lower of PD1 mRNA expression in PPCM relative to control. Furthermore, PD1 mRNA expression showed significant negative correlation with IFN-γ and CD3+, CD4+, CD8+ T lymphocytes, and proBNP as well as positive correlation with IL-4, IgG, IgM, IgA, C3, C4, and LVEF. The morphologic features of cells indicated that the PBLs in PPCM were in the state of activation. Therefore, decreased expression of PD1 mRNA led to LV dysfunction and functional dysregulation of negative costimulation on cellular immunity. This study provided the first findings that PD1 expression was decreased, which might disrupt immune homeostasis that enhanced cellular immunity was predominant over attenuated humoral immunity that may work in the etiopathogenesis of PPCM.

Enhanced Anti-tumor Reactivity of Cytotoxic T Lymphocytes Expressing PD-1 Decoy.

Programmed death-1 (PD-1) is a strong negative regulator of T lymphocytes in tumor-microenvironment. By engaging PD-1 ligand (PD-L1) on tumor cells, PD-1 on T cell surface inhibits anti-tumor reactivity of tumor-infiltrating T cells. Systemic blockade of PD-1 function using blocking antibodies has shown significant therapeutic efficacy in clinical trials. However, approximately 10 to 15% of treated patients exhibited serious autoimmune responses due to the activation of self-reactive lymphocytes. To achieve selective activation of tumor-specific T cells, we generated T cells expressing a dominant-negative deletion mutant of PD-1 (PD-1 decoy) via retroviral transduction. PD-1 decoy increased IFN-γ secretion of antigen-specific T cells in response to tumor cells expressing the cognate antigen. Adoptive transfer of PD-1 decoy-expressing T cells into tumor-bearing mice potentiated T cell-mediated tumor regression. Thus, T cell-specific blockade of PD-1 could be a useful strategy for enhancing both efficacy and safety of anti-tumor T cell therapy.

The anticancer immune response of anti-PD-1/PD-L1 and the genetic determinants of response to anti-PD-1/PD-L1 antibodies in cancer patients.

The programmed death-1 (PD-1), a coinhibitory receptor expressed on activated T cells and B cells, is demonstrated to induce an immune-mediated response and play a critical role in tumor initiation and development. The cancer patients harboring PD-1 or PD ligand 1 (PD-L1) protein expression have often a poor prognosis and clinical outcome. Currently, targeting PD-1 pathway as a potential new anticancer strategy is attracting more and more attention in cancer treatment. Several monoclonal antibodies against PD-1 or PD-L1 have been reported to enhance anticancer immune responses and induce tumor cell death. Nonetheless, the precise molecular mechanisms by which PD-1 affects various cancers remain elusive. Moreover, this therapy is not effective for all the cancer patients and only a fraction of patients respond to the antibodies targeting PD-1 or PD-L1, indicating these antibodies may only works in a subset of certain cancers. Thus, understanding the novel function of PD-1 and genetic determinants of response to anti-PD-1 therapy will allow us to develop a more effective and individualized immunotherapeutic strategy for cancer.

Lung CD8+ T Cell Impairment Occurs during Human Metapneumovirus Infection despite Virus-Like Particle Induction of Functional CD8+ T Cells.

Human metapneumovirus (HMPV) is a major cause of respiratory disease in infants, the elderly, and immunocompromised individuals worldwide. There is currently no licensed HMPV vaccine. Virus-like particles (VLPs) are an attractive vaccine candidate because they are noninfectious and elicit a neutralizing antibody response. However, studies show that serum neutralizing antibodies are insufficient for complete protection against reinfection and that adaptive T cell immunity is important for viral clearance. HMPV and other respiratory viruses induce lung CD8(+) T cell (TCD8) impairment, mediated by programmed death 1 (PD-1). In this study, we generated HMPV VLPs by expressing the fusion and matrix proteins in mammalian cells and tested whether VLP immunization induces functional HMPV-specific TCD8 responses in mice. C57BL/6 mice vaccinated twice with VLPs and subsequently challenged with HMPV were protected from lung viral replication for at least 20 weeks postimmunization. A single VLP dose elicited F- and M-specific lung TCD8s with higher function and lower expression of PD-1 and other inhibitory receptors than TCD8s from HMPV-infected mice. However, after HMPV challenge, lung TCD8s from VLP-vaccinated mice exhibited inhibitory receptor expression and functional impairment similar to those of mice experiencing secondary infection. HMPV challenge of VLP-immunized μMT mice also elicited a large percentage of impaired lung TCD8s, similar to mice experiencing secondary infection. Together, these results indicate that VLPs are a promising vaccine candidate but do not prevent lung TCD8 impairment upon HMPV challenge. Human metapneumovirus (HMPV) is a leading cause of acute respiratory disease for which there is no licensed vaccine. Virus-like particles (VLPs) are an attractive vaccine candidate and induce antibodies, but T cell responses are less defined. Moreover, HMPV and other respiratory viruses induce lung CD8(+) T cell (TCD8) impairment mediated by programmed death 1 (PD-1). In this study, HMPV VLPs containing viral fusion and matrix proteins elicited epitope-specific TCD8s that were functional with low PD-1 expression. Two VLP doses conferred sterilizing immunity in C57BL/6 mice and facilitated HMPV clearance in antibody-deficient μMT mice without enhancing lung pathology. However, regardless of whether responding lung TCD8s had previously encountered HMPV antigens in the context of VLPs or virus, similar proportions were impaired and expressed comparable levels of PD-1 upon viral challenge. These results suggest that VLPs are a promising vaccine candidate but do not prevent lung TCD8 impairment upon HMPV challenge.

The function of a novel immunophenotype candidate molecule PD-1 in chronic lymphocytic leukemia

Programmed death-1 (PD-1) is a negative receptor expressed on lymphocytes including malignant B cells in chronic lymphocytic leukemia (CLL). In this work, we found that patients with CLL had a higher expression of PD-1 transcript (PDCD1) than healthy volunteers (p < 0.0001). PDCD1 expression was comparable between CLL cells from accumulation (peripheral blood) and proliferation (bone marrow) disease compartments. In blood samples of patients with mutated IGHV genes PDCD1 expression was higher than with unmutated IGHV (p = 0.0299). We demonstrated that phosphorylation of SYK and LYN, key B-cell receptor signaling kinases, was independent of PD-1 expression in patients with CLL, while ZAP-70 phosphorylation in negative tyrosine residue 292 showed strong inverse correlation (r = − 0.8, p = 0.0019). No associations between five single nucleotide polymorphisms of PDCD1, their expressions and susceptibility to CLL were found. In conclusion, PD-1 might be an independent, universal marker of CLL cells and a part of their activated phenotype, and subsequently might modulate the function of ZAP-70.

T Cells in CTCL Have an Exhausted Phenotype While Cutaneous Dendritic Cells Display a Normally Activated Mature Phenotype

Background: Mycosis fungoides (MF) and Sézary syndrome (SS) represent the most common types of cutaneous T-cell lymphoma (CTCL). CTCL develops from clonally-expanded, effector/central memory CD4+ T cells in a background of chronic inflammation. The eliciting Ag(s) and how this inflammation contributes to the development and progression of CTCL remain important unknowns. Despite tumor-infiltrating CD8+ T cells in skin, the malignant CD4+ T-cell population persists, indicating that these CD8+ T cells cannot exert an effective anti-tumor response, potentially due to T-cell exhaustion, which has been observed in chronic viral infections and is associated with disease progression in hematologic malignancies like ATLL and CLL. Exhausted T-cells are characterized by immunoinhibitory molecules, like programmed death-1 (PD-1). Engagement of PD-1 by PD-Ligand (L)-1/L-2 transduces a signal that leads to inhibition of T-cell functions, but the cells are not deleted. PD-L1 is expressed on T cells, dendritic cells (DCs), and many tumor cells, whereas PD-L2 expression is limited to antigen-presenting cells. Although malignant CD4+ T cells in Sézary syndrome lesions express PD-1, the relevance of the PD-1/PD-L1/2 pathway in CTCL and the immune cells in CTCL that express PD-L1/L2 are not known.Methods: Epidermis and dermis of skin biopsies from consented CTCL pts (12) and healthy donors (3) were separated using dispase-II and incubated in RPMI-10% pooled human serum for 24 hrs. Migrated cutaneous T cells and DCs were phenotyped by flow cytometry for a variety of maturation markers and immune checkpoint molecules. In 3 pts skin findings were compared with matched PBMCs.Results: Freshly isolated cutaneous CD8+ T cells displayed distinct effector and memory subsets with a higher frequency of effector-memory (CD28-CD45RA-CCR7-) and terminally differentiated effector cells (CD28-CD45RA+CCR7-). In addition, CD8+ T-cells exhibited enhanced expression of PD-1, Lag-3, Tim-3, and ICOS. PD-1 was the receptor most overexpressed in CD8+ T cells compared with healthy controls. PD-1 expression on circulating CD8+ T cells was lower compared with skin-infiltrating CD8+ T-cells. In contrast, the malignant CD4+ T-cells expressed predominantly a central memory or transient memory subtype (CD28+CD45RA-CCR7+/-), with overexpression of PD-1, CTLA-4, Lag-3, and ICOS. Immune-suppressive CD3+CD4+FoxP3+CD127-Tregs were not increased in PBMCs of CTCL pts. Migrated DCs displayed an activated, mature phenotype expressing HLA-DR+, CD1a+/-, CD207 (Langerin)+/-, CD14+/-, CD11c+, CD83low/med, CD86low/med and PD-L1+/- phenotype.Conclusion: Both the malignant CD4+ T cells and tumor-infiltrating CD8+ T cells display an exhausted phenotype, while DC subsets display a normal activated phenotype. Our preliminary data imply a role for PD-1 and other checkpoint molecules like ICOS, Tim-3, Lag-3 in attenuating the anti-tumor response. Studies are underway in vitro to establish the function of PD-1, Lag-3, Tim-3, and ICOS on T cells in response to DC/LC stimulation to develop a rationale for therapeutic checkpoint blockade inhibitors to reverse the exhausted T cell phenotype and attendant lack of immune reactivity. DisclosuresNo relevant conflicts of interest to declare.

Regulation of Neuroinflammation through Programed Death-1/Programed Death Ligand Signaling in Neurological Disorders.

Immune responses in the central nervous system (CNS), which involve both resident glial cells and infiltrating peripheral immune cells, play critical roles in the progress of brain injuries and neurodegeneration. To avoid inflammatory damage to the compromised brain, the immune cell activities in the CNS are controlled by a plethora of chemical mediators and signal transduction cascades, such as inhibitory signaling through programed death-1 (PD-1) and programed death ligand (PD-L) interactions. An increasing number of recent studies have highlighted the importance of PD-1/PD-L pathway in immune regulation in CNS disorders such as ischemic stroke, multiple sclerosis, and Alzheimer’s disease. Here, we review the current knowledge of the impact of PD-1/PD-L signaling on brain injury and neurodegeneration. An improved understanding of the function of PD-1/PD-L in the cross-talk between peripheral immune cells, CNS glial cells, and non-immune CNS cells is expected to shed further light on immunomodulation and help develop effective and safe immunotherapies for CNS disorders.

Naturally Occurring PD-1+ Memory Phenotype CD8 T Cells Belong to Nonconventional CD8 T Cells and Are Cyclophosphamide-Sensitive Regulatory T Cells

CD8 T cells expressing memory markers exist in naive mice and are thought to be of heterogeneous origin. It was recently reported that among such memory-phenotype (MP) CD8 T cells in naive mice, those expressing programmed death-1 (PD-1) had immune regulatory activity, but their origin and relationship with other regulatory CD8 T cell subsets remain unclear. In the current study, we examined detailed characteristics and functions of PD-1(+) MP CD8 T cells in naive mice. Their expression pattern of surface molecules resembled that of exhausted CD8 T cells seen in chronic viral infection. However, PD-1(+) MP CD8 T cells were detected from neonatal periods, even in the thymus; thus, they are naturally occurring. By analyzing bone marrow chimera mice in which β(2)-microglobulin-deficient mice were used as the recipients, it was revealed that PD-1(+) MP CD8 T cells were positively selected by hematopoietic cells, indicating that they belong to nonconventional CD8 T cells. However, in contrast to majority of MP CD8 T cells, PD-1(+) MP CD8 T cells were IL-15 independent. PD-1(+) MP CD8 T cells showed the fastest cell cycling among various T cell subsets in naive mice, which was consistent with the highest sensitivity to cyclophosphamide (CP) treatment. Importantly, PD-1(+) MP CD8 T cells were able to suppress delayed-type hypersensitivity response that was augmented by CP treatment. Taken together, our data indicate that the naturally occurring PD-1(+) MP CD8 T cells in naive mice are a unique subset of nonconventional CD8 T cells and represent the CP-sensitive suppressor CD8 T cells.

Upregulation of circulating soluble programmed death-1 is associated with genetic variants in patients with rheumatoid arthritis

Event Abstract Back to Event Upregulation of circulating soluble programmed death-1 is associated with genetic variants in patients with rheumatoid arthritis Cuiping Liu1, Juean Jiang2, Li Gao2, Ting Wang2, Min Wu3, Ting Xu3 and Xueguang Zhang1* 1 The First Affiliated Hospital of Soochow University, Jiangsu Institute of Clinical Immunology, China 2 Soochow University, Medical Biotechnology Institute, China 3 The Third Affiliated Hospital of Soochow University, Department of Rheumatology, China The Programmed death 1 (PD-1) gene is a critical regulator of T-cell activation and is also an important therapeutic target for autoimmune diseases. It had been showed that the human PD-1 gene has 5 splice variants, one of which is a soluble form lacking transmembrane domains. However, little is known about the regulation and the functional properties of soluble PD-1(sPD-1) variants. To better understand how sPD-1 could be involved in autoimmunity, we set out to characterize biochemical and functional properties of sPD-1. We first developed a specific, quantitative ELISA and then used it to detect the presence sPD-1 in serum and joint fluids from patients with rheumatoid arthritis (RA) and osteoarthritis (OA). The levels of sPD-1 occurred at high concentrations in sera and synovial fluid of RA patients and correlated with titers of rheumatoid factor,swollen joint counts and DAS28 score in RA patients. Further characterization of soluble PD-1 revealed that it could functionally block the regulatory effect of membrane-bound PD-1 on T cell activation. Next, in correlation with their inflammatory status, we identified IFN-γ,TNF-α and IL-17 as inducers of sPD-1. Finally, the PDCD1+ 6370 single polymorphisms was found as a regulator of sPD-1 levels, serum sPD-1 levels in RA patients with GG genotype were significantly higher than those in AA genotype. Takentogether, the mechanism of antagonism of the function of PD-1 by soluble PD-1 may have important clinical relevance in the understanding of RA pathology. Acknowledgements This study was supported by the National Natural Science Foundation of China (Grants: 30930085,81001337 , 31170834). Keywords: soluble PD-1, costimulatory molecule, SNP, Autoimmunity, ra Conference: 15th International Congress of Immunology (ICI), Milan, Italy, 22 Aug - 27 Aug, 2013. Presentation Type: Abstract Topic: Immune-mediated disease pathogenesis Citation: Liu C, Jiang J, Gao L, Wang T, Wu M, Xu T and Zhang X (2013). Upregulation of circulating soluble programmed death-1 is associated with genetic variants in patients with rheumatoid arthritis. Front. Immunol. Conference Abstract: 15th International Congress of Immunology (ICI). doi: 10.3389/conf.fimmu.2013.02.00857 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 25 Jun 2013; Published Online: 22 Aug 2013. * Correspondence: Prof. Xueguang Zhang, The First Affiliated Hospital of Soochow University, Jiangsu Institute of Clinical Immunology, Suzhou, Please Select, 215006, China, xueguangzh@yahoo.com.cn Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Cuiping Liu Juean Jiang Li Gao Ting Wang Min Wu Ting Xu Xueguang Zhang Google Cuiping Liu Juean Jiang Li Gao Ting Wang Min Wu Ting Xu Xueguang Zhang Google Scholar Cuiping Liu Juean Jiang Li Gao Ting Wang Min Wu Ting Xu Xueguang Zhang PubMed Cuiping Liu Juean Jiang Li Gao Ting Wang Min Wu Ting Xu Xueguang Zhang Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

The PD-1/PD-L1 Pathway in Human Pathology

T-cell activation is dependent on signals delivered through the antigen-specific T-cell receptor and accessory receptors on T-cells. Integration of signals through this family of costimulatory and inhibitory receptors and their ligands regulates the balance between T-cell activation, tolerance, and immunopathology. Programmed death 1 (PD-1) and its ligands, PD-L1 and PD-L2, deliver inhibitory signals and exert a vital and diverse range of immunoregulatory roles in T-cell activation, tolerance, and immune-mediated tissue damage. In this review, we revisit current understanding of the immunoregulatory functions of PD-1 and its ligands and their involvement in immune-mediated diseases.